Google Cloud Router Documentation

Google Cloud Router enables you to dynamically exchange routes between your Virtual
Private Cloud (VPC) and on-premises networks by using
Border Gateway Protocol (BGP).
For example, if you use a Cloud VPN tunnel to connect your networks, you can
use a Cloud Router to establish a BGP session with your
on-premises router over your VPN tunnel. The Cloud Router
automatically learns new subnets in your VPC network and announces them to your
on-premises network.